Re: Sharp LC-58Q7330U No Backlight
Thank you so much and also for the link. Your link at the store through Aliexpress was cheaper than the store that I was going through.
Misterfixit
Member
Last Activity: 07-26-2023, 12:27 PM
Joined: 04-27-2017
Location: Northville, Michigan
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Sharp LC-58Q7330U No Backlight
This set has the known reputation of failed led backlights. The set does not turn on, but when plugged in, the power led stays lit for about 5 seconds followed by two short blinks and then it repeats itself. While shinning a flashlight on the screen, you can make out the Sharp logo, then it goes out and repeats the cycle. I measured some voltages across the led backlight connector. What has me puzzled is that when I place the negative lead of my vom on the led backlight pin connector (in which the black wire going to the leds was), I measure as high as -228volts, and then it falls to -95 volts... -
Re: sharp LC-50LB601U No backlight
Unfortunately, to get to this connector, you have to disassemble the whole front end of the set. I could have simply soldered jumper wires across this connector once I had the whole lcd, diffusers, etc off, but I decided to just replace all of the led rows. Thanks againLeave a comment:
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Re: sharp LC-50LB601U No backlight
Thanks Lotas for all you help. I ordered the led strips from Ali express. They came in about a week ago and i just installed them. The set now works as though it is like new.
After placing the old led strips on the bench, I started testing them. It turns out that the leds were all working properly. It was the individual connector between the each strip that makes each row, was bad. As I wiggled the connector, the led strips all lit up. There are 4 individual rows of leds (each row has 8 leds, total 32 leds for this set)that are used in this...Leave a comment:
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Re: sharp LC-50LB601U No backlight
Yes Lotas, the voltage rating of capacitor c8605 is 50 volts. Also, C8634,c8635,c8629 and c8630 is also 50 volts. By the fact that you sent me the Ali express link for the backlight led strips, do you feel pretty confident that I have a serious of failed led backlights? Thank youLeave a comment:
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Re: sharp LC-50LB601U No backlight
Thanks lotus, I am using a fluke vom, when I turn on the set using the remote control on your suggested led connector points, I only see 30 volts on both of the measurements. It could be that the protection circuit is way faster than what the digital meter can display. Before, I tear into the led backlights, is there anything else you can think of to verify it is the led backlights and not the power supply board. ThxLeave a comment:
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Re: sharp LC-50LB601U No backlight
Here is a picture of the complete back of the power supply to the above post....Leave a comment:
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sharp LC-50LB601U No backlight
I have a sharp LC-50LB601U that has no backlight. It starts up fine, and has sound, however, I can only see the screen using a flashlight. I took the tv back off and measured voltages at the power supply connector CN-8601. As you can see by the picture, the led connector has 2 sets of 2 red wires and 2 sets of black wires going to the led backlights. Between each set of black wires and corresponding red wires, I measure 30 volts (pins 1 and 4) and 30 volts from pins 8 and 12. From ground to each set of red wires ( pins 1 and 12 to ground), I measure 35 volts. This voltage seems very low compared...Last edited by Misterfixit; 04-04-2023, 01:50 PM. -
Re: Vizio M502i-B1 won't turn on
I replaced the main circuit board and the set turned on and everything is working fine again. While I had the back off and the set was working properly, I did put a volt meter on the power supply 24 volt pin out connection to see if anything changed. The voltage remained the same as before (19.6 volts). I also checked one of the electrolytic capacitors on the led driver board. As I recall, originally the voltage across each of them was 19.6 (the original 24 volt supply). With the new main board in and the set working, the voltage on c820 was 25.75...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
I ordered the main circuit board and will report back once i receive and install it.Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Budwich: I still have 11.58 volts (circuit board states it should be 12 volts) on the connector CN9101 on the power supply board.This connector and associated cable go directly to the main circuit board. On the main circuit board, there are two cables that go to the t-con board. At one of the cables and connector coming into the t-con board from the main circuit board, there is a designation on the t-con board that identifies it as j101. Close to this connector is the t-con fuse designated as F1. I measured conductivity across this fuse and it checked...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Thanks again everyone for your patience. Based on your input, I did locate the fuse (F1) on the t-con board near J101. The fuse Checked good. However, there was no voltage present on the fuse terminals of F1 when the set was plugged in. So, if the 12 volts to the t-con board is controlled by the main circuit board microprocessor, then I also suspect that the main control board is suspect.Leave a comment:
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Re: Vizio M502i-B1 won't turn on
I removed the metal covering plate that covers the t-con board and attaches to tv stand. I looked very close for any type of fuse or fuse designation on the t-con circuit board. The board is so tiny and is hard to look at the smd parts even with a magnifying glass. I didn't see any fuse. I also unplugged the two connectors to the t-con board. Then, I energized the TV set, and nothing changed (i.e., no sound or standby light, etc). I took some pictures of the board hoping to review them later thru magnification setting of iPhone. I also, removed the...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Thanks budm and budwich for your quick response. I got briefly excited after measuring the open Zener diode on the on/off board, thinking, that perhaps, I was on to something. Well, after reading your responses, it's sounds like the voltages that I measured are in line with "Active low (off =>2 volts DC, on =<1 volt"
Now, I am back to square one, thinking about, how can I can locate the "bl-on"pin and measure the voltage. Does it make any sense, to measure each wire to ground in the connector from the main circuit...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Dskall: I did check it several times. I can absolutely tell you the diode shown as zdo0231 is open (infinite resistance in both directions using the diode setting in my digital vom). I suspect that with out the zenor diode operating, the supply voltage from the main circuit board, gets dragged down when the push button is depressed. However, I suspect with the zenor diode operating correctly, the voltage is allowed to stay above a certain value which feeds back to the main board. When the push button is depressed, it changes this voltage and the...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Rely to dekall: I could not identify which pin or wire is associated with bl-on. So, imfllowed budwich's advice and tried to focus on the on/off board. As I previously mentioned, the on/off button had no effect on turning the set on. I believe that zenor diode (zdo0231) is open on the on/off circuit board. I would like to substitute the zenor diode and try to see if this will turn the set on. So, can any one recommend the zenor diode value( perhaps 1.85 volts)Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Here is a drawing of the on/off circuit board that I drew from taking point to point resistance readings off. The Zenor diode appears to be open. I was wondering if any one had a suggestion as to what the zenor diode voltage rating should be. The incoming voltage is 2.85 volts. What do you suggest zenor diode zdo321 should be? The other question is what had happened just before the set quit. We had experinced power outages in the area where the power went on and off seven times. After the the power was restored, we were watching the tv and it went...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Budwich:here is a picture of the on/off circuit board. For starters,the voltage on the two wires from the main circuit to the on/off board is 2.85volts. When the on/off button was depressed, the vintage drops to .3 volts. When the board is disconnected, the resistance on the two pins goes from infinte resistance to 479 ohms when the button is depressed. I suspect the zenor diode is open. I also drew a schematic of the board which I will send next...Leave a comment:
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Re: Vizio M502i-B1 won't turn on
Does anyone have any further suggestions/advice for me to try?Leave a comment:
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Re: Vizio M502i-B1 won't turn on
I measured the on/off pin on connector cn9101 it was 1.14 volts. The voltage at this pin does not change whether the on off button is depressed or the remote control power button is depressed.Leave a comment:
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